CTCL is a group of T lymphomas which primarily involve the skin. The CTCL group namely comprises transformed Mycosis Fungoides (abbreviated into transformed MF), Sézary Syndrome (abbreviated into SS), Lymphomatoide Papulosis (abbreviated into LP), and CD30+ lymphomas. Transformed MF is characterized by skin invasion of clonally-derived malignant T lymphocytes that phenotypically resemble mature T helper cells. LP and CD30+ lymphomas also develop in the skin. More aggressive forms of CTCL develop when the malignant cells become non-epidermotropic, and are associated with extra-cutaneous involvement. SS is a more aggressive form of CTCL that is characterized by a clonal expansion of CD4+/CD45RO+ T cells and the appearance of these malignant T cells in the blood. Most CTCL are CD4+ CTCL, but some rare CD8+ CTCL cases exist.
The biology of CTCL disease remains poorly understood, as it is difficult to identify the malignant cells, due to the lack of specific cell surface markers. In cutaneous lesions, it is therefore difficult to distinguish CTCL cells from reactive infiltrating (non-tumoral) T lymphocytes.
Diagnosis of T lymphomas such as CTCL is at present time mainly based on cytological and histological observations of the presence or absence of tumoral cells in a sample collected from a suspected body area (observation of histopathological aspect on skin biopsis and/or presence of SS cells in the blood, via detection of cells showing a cerebriform nucleus). Such a diagnosis method is not fully reliable, notably at the early stages of the transformation of skin lymphocytes into malignant lymphocytes. Such a diagnosis method does also not enable to stage the disease. Technically speaking, it is also time-consuming.
Today, therapy of CTCL is tentatively achieved by induction of tumoral cell apoptosis via non specific chemotherapy.
There is therefore still a need for more accurate and appropriate solutions to the problem of the diagnosis and therapy of diseases involving the proliferation of malignant T cells, such as CTCL.